This invention pertains to the field of dry carbonating agents and the means for preparing them. More particularly, the present invention relates to methods of preparing, isolating and using dry, stable complexes of carbohydrate/metal bicarbonate which contain bound water. These carbon dioxide-carrying complexes can be admixed with other dehydrated materials and such mixtures can thereafter be reconstituted as carbonated beverages or used in other applications in which effervescence is desired.
Compounds which have been utilized as carbonating agents in dry form have generally included inorganic carbonates or bicarbonates, the most common of which is sodium bicarbonate. Other agents have included sodium carbonate, potassium carbonate and calcium carbonate. However, these substances have generally been found to be unacceptable when present in amounts sufficient to provide a desirable level of carbonation to a beverage because upon release of carbon dioxide by contact with an acid, the corresponding sodium, potassium and calcium salts result in an undesirable brackish and/or metallic taste.
More particularly, sodium bicarbonate provides a mole ratio of carbon dioxide to sodium ion of at most 1:1, whereas sodium carbonate releases only one mole of carbon dioxide for every two moles of sodium ion. The use of sodium salts, moreover, may not be desirable in certain instances. Potassium carbonate also yields two moles of the potassium ion for each mole of carbon dioxide released and again results in a salty taste.
Calcium carbonate too only provides a mole ratio of 1:1 of carbon dioxide to calcium ion upon release and while it does not produce a distinctly salty taste, in high concentrations it imparts a metallic off-flavor to beverages. It is also insoluble in water, which further reduces its desirability as a carbonating agent. While calcium bicarbonate could be used to provide a theoretical mole ratio of carbon dioxide to calcium ion of 2:1, free calcium bicarbonate is unstable, and it is believed that it has never been isolated in dry form.
Accordingly, as a means of avoiding the presence of metallic ions in carbonating agents and their corresponding disadvantages, organic carriers for carbon dioxide have been sought. In U.S. Pat. No. 3,441,417, a hydroxy carboxylic acid is reacted with phosgene gas to obtain an ester carbonating agent. U.S. Pat. No. 3,649,298 describes methods of making disodium salts of N-carboxy amino acids to be used in combination with anhydrides in beverage concentrates. This process also requires phosgene. The use of phosgene, however, produces products which may cause toxicological problems. Consequently, these products are also undesirable.
A process for the preparation of a L-lysine carbamate as an organic carbon dioxide carrier for effervescent compositions was described in UK Patent Application GB No. 2,037,760 A.
In non-food effervescent applications, while the level of metallic salt content may not be of critical importance, a compound with only a 1:1 mole ratio of carbon dioxide to metallic ion may be economically undesirable because of the amount of such carbonating agent required to achieve a particular carbonation effect.